Single use syringe and plunger rod locking device therefor

ABSTRACT

A single use syringe assembly is provided as well as a locking element for such an assembly. The single use syringe assembly includes a barrel, a plunger rod assembly and a locking element positioned within the barrel. The locking element includes one or more barbs for engaging the inside surface of the barrel. The barbs prevent the locking element from moving proximally within the barrel, but allow its distal movement therein with the plunger rod assembly. A spring member may be provided for urging the barbs towards the inside surface of the barrel. The barbs are preferably positioned on the edge portions of opposing legs that form part of the locking element.

This Application claims benefit of U.S. provisional application No.60/324,434 filed Sep. 24, 2001.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The field of the invention relates to single use syringes and lockingdevices for locking the plunger assemblies of such syringes.

2. Brief Description of the Related Art

In the United States and throughout the world the multiple use ofhypodermic syringe products that are intended for single use only isinstrumental in drug abuse and more particularly in the transfer ofcontagious diseases. Intravenous drug users who routinely share andreuse syringes are a high risk group with respect to the AIDS virus.Also, the effects of multiple use are a major concern in third worldcountries where repeated use of syringe products may be responsible forthe spread of many diseases. Reuse of single use hypodermic syringeassemblies is also instrumental in the spread of drug abuse even in theabsence of infection or disease.

Many attempts have been made to remedy this problem. Some of theseattempts have required a specific act to destroy the syringe after useeither by using a destructive device or providing a syringe assemblywith frangible zones so that the syringe could be rendered inoperable bythe application of force. Other attempts have involved the inclusion ofstructure which would allow the destruction or defeating of the syringefunction through a conscious act by the syringe user. Although many ofthese devices work quite well, they do require the specific intent ofthe user followed by the actual act to destroy or render the syringeinoperable. None of these devices is effective with a user having thespecific intent to reuse the hypodermic syringe.

Single use hypodermic syringes that become inoperative or incapable offurther use automatically without any additional act on the part of theuser have been developed. One such syringe is disclosed in U.S. Pat. No.4,961,728. The syringe disclosed in this patent includes a lockingelement positioned in the syringe barrel. The locking element includesproximally and outwardly facing barbs that engage the inner surface ofthe syringe barrel and an inwardly facing driving edge adapted tointeract with the plunger rod to move the locking element along thebarrel as the stopper is advanced. The plunger rod includes a ledgepositioned at a distance from the proximal side of a support wall thatapproximates the length of the locking element. The driving edge of thelocking element engages the ledge, thereby ensuring that the lockingelement moves distally with the plunger rod and stopper.

U.S. Pat. Nos. 5,021,047, 5,062,833 and 5,562,623 disclose single usesyringes having plunger rods that have teeth or ridges and lockingelements that engage the teeth or ridges. The locking elements of thesesyringes also include outwardly extending teeth or prongs that engagethe inside surface of the syringe barrel. The plunger rods of thesesyringes can be retracted to draw fluid into the syringe barrel whilethe locking elements remain stationary. Distal movement of the plungerrods causes the fluid to be expelled, the locking elements movingdistally with the plunger rods and substantially preventing furtherplunger rod retraction.

SUMMARY OF THE INVENTION

A locking element for a single use syringe is provided. The lockingelement includes a base including a generally trough-shaped body havinga longitudinal axis. A first leg extends from the base and issubstantially parallel to the longitudinal axis. A second leg extendsfrom the base in opposing relation to the first leg. Each leg includesone or more barbs. Each leg further includes an end portion that extendsgenerally toward the longitudinal axis. A spring element is attached tothe base for urging the barbs in a selected direction. The barbs arepreferably located on the outer edges of the first and second legs.

A single use syringe assembly with a needle cannula in accordance withthe invention includes a barrel having an inside surface defining achamber for retaining fluid. The barrel has an open proximal end and adistal end having a passageway in communication with the chamber. Aplunger rod assembly is provided for use in conjunction with the barrel.The plunger rod assembly includes an elongate body portion having aproximal end, a distal end, and a stopper mounted to the elongate bodyportion proximate the distal end. The stopper is slidably positioned insubstantially fluid tight engagement with the inside surface of thebarrel. The elongate body portion of the plunger rod assembly extendsoutwardly from the open proximal end of the barrel. A generallytrough-shaped locking element is positioned within the barrel. Thelocking element defines a channel through which the elongate bodyportion of the plunger rod assembly extends. One or more barbs extendfrom the locking element. The barbs engage the inside surface of thebarrel for substantially preventing the locking element from movingproximally with respect to the barrel. The locking element also engagesthe elongate body portion of the plunger rod assembly such that thelocking element is movable towards the distal end of the barrel as theplunger rod assembly is advanced. A spring member is attached to thelocking element and urges the one or more barbs towards the insidesurface of the barrel.

A single use syringe assembly is further provided that includes a barrelhaving an inside surface defining a chamber for retaining fluid, aplunger rod assembly, a needle cannula for hypodermic injection, and alocking element. The plunger rod assembly includes an elongate bodyportion having a proximal end, a distal end and a stopper mounted to theelongate body portion. The stopper is slidably positioned insubstantially fluid tight engagement with the inside surface of thebarrel. The locking element is positioned within the barrel. It includesfirst and second opposing walls and a third wall that connects them. Afirst leg extends from the first wall and a second leg extends from thesecond wall. A first barb extends from the first leg of the lockingelement while a second barb extends from the second leg thereof. It willbe appreciated that one or more barbs may extend from the legs of thelocking element. Each leg includes an end portion engageable with thebody portion of the plunger rod assembly. The locking element canaccordingly be moved distally with the plunger rod assembly along thesyringe barrel. The barbs substantially prevent the locking element frommoving proximally therein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded, perspective view showing a single use syringeassembly according to the invention;

FIG. 2 is a top perspective view of the syringe assembly prior to use;

FIG. 3 is a top perspective view showing the syringe assembly followingretraction of the plunger rod assembly thereof;

FIG. 4 is a cross-sectional view of the syringe assembly with theplunger rod assembly in the position shown in FIG. 2;

FIG. 5 is a cross-sectional view thereof showing the plunger rodassembly in the position shown in FIG. 3;

FIG. 6 is a cross-sectional view thereof showing the plunger rodassembly in a locked position following the injection stroke;

FIG. 7 is a cross-sectional view of the syringe of FIG. 4 taken alongline 7-7.

FIG. 8 is a top plan view of a preform of a locking element;

FIG. 9 is a top plan view of a locking element for the single usesyringe assembly;

FIG. 10 is a side elevation view of the locking element, and

FIG. 11 is an end view of the locking element.

DETAILED DESCRIPTION OF THE INVENTION

There is shown in the drawings and will be described in detail herein apreferred embodiment of the invention with the understanding that thepresent disclosure is to be considered as exemplary of the principles ofthe invention and is not intended to limit the invention to theembodiment illustrated.

Referring first to FIGS. 1-3, a single use syringe assembly 20 includesa barrel 22 having an inside surface 24 defining a chamber 26 forretaining fluid. The barrel 22 includes an open end 28 and a distal end30 having a passageway 32 therethrough in communication with thechamber. A needle cannula 34 projects outwardly from the distal barrelend. The needle cannula has a lumen (not shown) therethrough in fluidcommunication with the passageway and a sharpened distal tip. Thesyringe assembly of the present invention is preferably used with aneedle cannula that is attached to the distal end of the barrel by anadhesive or other suitable means. It will be appreciated that theinvention could be applied to syringe assemblies having removableneedle/hub assemblies, or fixed or removable blunt cannulas.

As used in the preceding paragraph and hereafter, the term “distal end”refers to the end furthest from the person holding the syringe assembly.The term “proximal end” refers to the end closest to the holder of thesyringe assembly. In the preferred embodiment, the proximal end of thebarrel 22 includes a flange 36 to facilitate handling and positioning ofthe syringe assembly and to maintain the relative position of the barrelwith respect to the plunger rod during filling and medicationadministration.

A plunger assembly 38 includes a plunger rod 40 having an elongate bodyportion 42. The distal end of the elongate body portion includes aprojection having an enlarged end 44. A stopper 45 having a recesstherein is affixed to this end. A disc-shaped flange 46 is provided atthe proximal end of the plunger rod for allowing the user to apply theforce necessary to move the plunger rod with respect to the barrel. Theelongate body portion 42 includes several sections between the proximaland distal ends thereof. A first section 42A thereof is substantiallycylindrical. The distal end of this section adjoins an enlarged plungerrod surface that functions as a stop surface 48 as described hereafter.A second section 42B adjoins the proximal end of the first section, andis also substantially cylindrical. The second section is larger indiameter than the first section, and accordingly defines a shoulder 50at the proximal end of the first section. A third section 42C extendsbetween the second section 42B and the disc-shaped flange 46. A secondshoulder 52 adjoins the proximal end of the second section 42B, andseparates the second and third sections.

A locking element 54 is positioned within the barrel 22. In accordancewith the preferred embodiment, the locking element is generallytrough-shaped. The locking element defines a channel through which theelongate body portion 42 of the plunger rod 40 extends. It will beappreciated that the locking element can be U-shaped in cross section orotherwise similarly configured, all of which should be consideredgenerally trough-shaped as the term is used herein.

The locking element includes a base 56 that includes a bottom wall 58and first and second opposing side walls 60, 62. A first leg 64 extendsproximally from the first wall and a second leg 66 extends proximallyfrom the second wall. The legs 64, 66 are also in opposing relation. Aspring element 68 in the form of a third leg extends proximally from thebottom wall 58.

Each of the legs 64, 66 includes an end portion that is angled generallytowards a longitudinal axis extending through the channel defined by thelocking element. They further include inner and outer edges. (The terms“inner” and “outer” are relative terms as used herein.) The inner edgesthereof are substantially adjacent to the spring element. Barbs 70, 72are integral with the outer edges of the first and second legs. Thespring element 68 includes a pair of bends 68A, 68B therein. Itaccordingly extends beneath the plane of the bottom wall 58 of the base56, as best shown in FIG. 10.

The locking element is preferably formed from a thin sheet of metal suchas stainless steel. It is preformed into the flat configuration shown inFIG. 7. The broken lines show the folds that are made in the flatsubstrate 74 to form the locking element 54 shown in FIGS. 7 and 9-11.The dimensions of the locking element are selected in accordance withthe barrel and plunger rod assembly with which it is to be used.

The syringe assembly is easily constructed from the component partsthereof. The locking element is positioned on the section 42B of theplunger rod 40 such that the angled end portion of the legs 64, 66adjoin the shoulder 52 at the proximal end of this section. The legs 64,66 and spring member extend proximally, and the barbs 70, 72 are angledproximally with respect to the plunger rod. The plunger rod/lockingelement assembly is then inserted into the barrel 22 through theproximal end thereof. As the assembly is moved distally within thebarrel, the angular orientation of the barbs allows them to slide alongwhile engaging the inside surface 24 of the barrel. The locking elementmoves distally with the plunger rod due to the engagement of the ends ofthe legs 64, 66 with the shoulder. The plunger rod/locking elementassembly is moved distally to the positions shown in FIGS. 2 and 4 wherethe stopper engages the end wall of the barrel. The syringe assembly isthen ready for use or storage.

In use, the plunger rod assembly 38 is retracted from the position shownin FIG. 4 to the position shown in FIG. 5 in order to draw fluid throughthe needle cannula 34 and passageway 32 and into the chamber 26 of thebarrel 22. The locking element 54 remains stationary during suchretraction, and the plunger rod assembly is moved proximally withrespect to both the barrel 22 and the locking element. This is due tothe engagement of the barbs 70, 72 with the inside surface 24 of thebarrel. The barbs are preferably made from a harder material than thebarrel, which enhances their ability to resist proximal movement. Thebarbs are resiliently urged by the spring member towards the insidesurface 24 of the barrel, further enhancing their effectiveness.

Retraction of the plunger rod assembly 38 is limited by the lockingassembly. As shown in FIG. 5, the stop surface 48 on the plunger rod 40engages the distal end of the locking element 54. As the locking elementcannot be moved proximally, further retraction of the plunger rodassembly is not possible. The amount of fluid that can be drawn into thechamber 26 is accordingly limited by the distance between the stopsurface 48 and the second shoulder 52 as well as the length of thelocking element. It will be appreciated that the distance between thestop surface 48 and second shoulder 52 and the length of the lockingelement 54 can be chosen to meet the needs of particular applications.

The end portions of the legs 64, 66 of the locking element adjoin thefirst shoulder 50 when the plunger rod assembly is retracted to theposition shown in FIG. 5. The distance between the first shoulder 50 andthe stop surface 48, being substantially the same as the distancebetween the distal end of the locking element and the proximal endportions of the legs, causes the locking element to be substantiallyimmovable with respect to the plunger rod assembly. As discussed above,the locking element is substantially immovable in the proximal directionwithin the barrel due to the engagement of the barbs 70, 72 with theinside surface of the barrel 22.

Once the fluid has been drawn into the barrel from a vial or other fluidsource, the needle cannula can be removed from the fluid source and usedfor injection. During the injection of a patient, the plunger assembly38 and locking element both move distally from the positions shown inFIG. 5 to the positions shown in FIG. 6. In FIG. 6, the stopper 45 againadjoins or engages the end wall of the barrel 22. The locking element 54remains positioned between the stop surface 48 and the first shoulder50. Both the plunger rod assembly 38 and the locking element aresubstantially immovable from their positions. The syringe assembly 20accordingly cannot be reused.

The syringe barrel of the present invention may be constructed of a widevariety of rigid materials with thermoplastic materials such aspolypropylene and polyethylene being preferred. Similarly, thermoplasticmaterials such as polypropylene, polyethylene and polystyrene arepreferred for the plunger rod. A wide variety of materials such asnatural rubber, synthetic rubber and thermoplastic elastomers aresuitable for the stopper. The choice of stopper material will depend oncompatability with the medication being used. In the preferredembodiment of this invention, the stopper 45, made of medical graderubber, includes a partially hollow interior with an undercut ledgewhich is snap fit over complementary structure 44 on plunger rod 40 tosecure the stopper to the plunger rod. The stopper and plunger rod mayalso be integrally formed of the same material or different materials,or secured together in other suitable ways.

As previously recited, it is preferable that the locking element befabricated from a material which is harder than the barrel so that thelocking barbs may effectively engage the barrel. Resilient spring likeproperties are also desirable along with low cost dimensionallyconsistent fabrication. With this in mind, sheet metal is the preferredmaterial for the locking element with stainless steel being preferredfor medical applications. Although the locking element of the preferredembodiment is fabricated from a single sheet, it is within the purviewof the instant invention to include locking elements made of other formsand/or containing multiple parts and materials.

Thus, it can be seen that the present invention provides a simple,reliable, easily fabricated, single use syringe which becomes inoperableor incapable of further use without any additional act on the part ofthe user.

1. A single use syringe assembly comprising: a barrel having an insidesurface defining a chamber for retaining fluid, and open proximal endand a distal end having a passageway in communication with said chamber;a plunger rod assembly including an elongate body portion having aproximal end, a distal end, first and second adjoining portions, saidfirst portion being distal of said second portion and having a smallerdiameter than said second portion, a first shoulder separating saidfirst and second portions, and a stop surface at the distal end of saidfirst portion, and a stopper mounted to said elongate body portionproximate said distal end, said stopper being slidably positioned insubstantially fluid tight engagement with said inside surface of saidbarrel, said elongate body portion extending outwardly from said openproximal end of said barrel; and a generally trough-shaped lockingelement positioned within said barrel, said locking element defining achannel, a distal end and a proximal end, said elongate body portion ofsaid plunger rod assembly extending through said channel; one or morebarbs extending from said locking element, said one or more barbsengaging said inside surface of said barrel for substantially preventingsaid locking element from moving proximally with respect to said barrelbut allowing movement of said locking element towards said distal end;wherein said distal end of said locking element is engageable with saidstop surface and said proximal end of said locking element is engageablewith said first shoulder such that said locking element is movabletowards said distal end of said barrel as said plunger rod assembly isadvanced, and a spring member attached to said locking element andurging said one or more barbs towards said inside surface of saidbarrel.
 2. A single use syringe assembly as described in claim 1 whereinsaid locking element includes first and second edges, said one or morebarbs extending from said edges, and said spring member being integralwith said locking element.
 3. A single use syringe assembly as describedin claim 2 wherein said locking element includes a base and first andsecond legs extending from said base, said first and second legs beingin substantially opposing relation and having end portions engageablewith said elongate body portion of said plunger rod, said spring membercomprising a third leg extending from said base between said first andsecond legs.
 4. A single use syringe assembly as described in claim 3wherein said first and second legs include inner edges adjoining saidthird leg and outer edges, said outer edges of said first and secondlegs including one or more barbs.
 5. A single use syringe assemblycomprising: a barrel having an inside surface defining a chamber forretaining fluid; a plunger rod assembly including an elongate bodyportion having a proximal end, a distal end, first and second adjoiningportions, said first portion being distal of said second portion andhaving a smaller diameter than said second portion, a first shoulderseparating said first and second portions, and a stop surface at thedistal end of said first portion, and a stopper mounted to said elongatebody portion, said stopper being slidably positioned in substantiallyfluid tight engagement with said inside surface of said barrel, saidelongate body portion extending outwardly from said barrel; a lockingelement positioned within said barrel, said locking element including abase including first and second opposing walls and a third wailconnecting said first and second walls, a first leg extending proximallyfrom said first wall, a second leg extending proximally from said secondwall, said first and second legs being in opposing relation, a firstbarb extending from said first leg and engaging said inside surface ofsaid barrel, a second barb extending from said second leg and engagingsaid inside surface of said barrel, said first leg including a first endportion engageable with said elongate body portion of said plunger rodassembly, said second leg including a second end portion engageable withsaid elongate body portion of said plunger rod assembly, said first andsecond inwardly extending end portion of said first and second legsbeing engageable with said first shoulder, said locking element beingengageable with said stop surface and said first and second barbs beingpositioned to substantially prevent said locking element from movingproximally in said barrel, but allowing said locking element to movedistally within said barrel.
 6. A single use syringe as described inclaim 5 including means for resiliently urging said first and secondbarbs towards said inside surface of said barrel.
 7. A single usesyringe as described in claim 6 wherein said means for resilientlyurging including a third leg extending proximally from said third wallof said base, each of said first and second legs includes asubstantially flat body having an inner edge substantially adjacent tosaid third leg and an outer edge, said first and second barbs extending,respectively, from said outer edges of said first and second legs.
 8. Asingle use syringe as described in claim 7 wherein said locking elementhas a generally trough-shaped configuration.
 9. A single use syringe asdescribed in claim 8 wherein said elongate body portion of said plungerrod assembly includes a second shoulder proximal of said first shoulder,said end portions of said first and second legs being engageable withsaid second shoulder.
 10. A single use syringe as described in claim 9wherein the distance between said first shoulder and said stop surfaceis substantially the same as the length of said locking element.
 11. Asingle use syringe as described in claim 10 where in said lockingelement is formed from a substantially flat, integral sheet of metal.12. A single use syringe as described in claim 5 where in said lockingelement is formed from a substantially flat, integral sheet of metal.13. A single use syringe as described in claim 12 including a springmember extending proximally from said base and urging said barbs towardssaid inside surface of said barrel, wherein each of said first andsecond legs includes a substantially flat body having inner and outeredges, said first and second barbs extending, respectively, from saidouter edges of said first and second legs, said inner edges of saidfirst and second legs being adjacent to said spring member.
 14. A singleuse syringe as described in claim 13 wherein said locking element has agenerally trough-shaped configuration.
 15. A single use syringe asdescribed in claim 13 where said spring member includes a third legextending proximally from said third wall of said base, said third legincluding a bend therein.